This invention relates to alkylmethylsiloxane mixtures which are useful for softening and moisturizing skin. The mixtures comprise one or more alkylmethylsiloxane solvents of the structure [MeRSiO].sub.a [Me.sub.2 SiO].sub.b or R'Me.sub.2 SiO(MeRSiO).sub.w (Me.sub.2 SiO).sub.x SiR'Me.sub.2 and one or more alkylmethylsiloxane waxes of the structure R'Me.sub.2 SiO(Me.sub.2 SiO).sub.y (MeRSiO).sub.z SiMe.sub.2 R', wherein each R is independently a hydrocarbon of 6 to 30 carbon atoms, R' is methyl or R, a is 1-6, b is 0-5, w is 0-5 and x is 0-5, provided a+b is 3-6 and w is not 0 if R' is methyl. These mixtures form films on the skin which function as barriers to transepidermal water loss and, thus, soften the skin by virtue of its own moisture.
Alkylmethylsiloxane waxes are known in the art for skin care applications. For instance, Th. Goldschmidt AG in their product literature report that certain polysiloxane polyalkylene copolymers known as ABIL.RTM.-WAX 9800 and ABIL.RTM.-WAX 9801 have utility in applications such as day creams, all purpose creams and body lotions. The materials therein are described as soluble in cosmetic oils and waxes and are useful in protecting against aqueous media. The present inventors, however, have discovered that mixtures comprising alkylmethylsiloxane waxes with alkylmethylsiloxane solvents penetrate the skin faster, are more substantive to the skin surface, have improved aesthetics and spreading, and form more occlusive films on the skin than the waxes in conventional solvents.
U.S. Pat. No. 4,574,082 issued Mar. 4, 1986, describes cosmetic moisturizers containing dimethylpolysiloxanes in admixture with organopolysiloxanes such as polymethyloctylsiloxane and polymethyloctadecylsiloxane. This reference, however, is limited to dimethylpolysiloxane solvents which the present inventors have shown are less effective than the alkylmethylsiloxane solvents claimed herein.
Protective skin creams containing hydrocarbon substituted organosiloxanes are also described in United Kingdom Patent No. 737,134 granted Sep. 21, 1955. This reference, however, claims compounds in which the hydrocarbon radicals are at the end of the polymer chain rather than along its backbone. Moreover, this reference also fails to describe the incorporation of alkylmethylsiloxane solvents as in the present invention.
U.S. patent application Ser. No. 07/642,623 filed Jan. 17, 1991 and assigned to the same assignee hereof also discloses alkylmethylsiloxanes for skin care. The application, however, fails to describe the incorporation of alkylmethylsiloxane solvents as claimed and disclosed herein.
Krzysik in U.S. Pat. No. 4,973,476 describes mixtures of a functional siloxane (which may be an alkylmethylsiloxane) and a volatile siloxane (which may be an alkylmethylsiloxane). Such mixtures, however, are described therein as being useful for hair conditioning.
Accordingly novel skin care formulations and methods are provided herein in which alkylmethylsiloxane waxes are mixed with alkylmethylsiloxane solvents and applied to the skin as moisturizing agents.